1. Field of the Invention
The present invention relates to an outboard motor including an engine, an engine cover forming an engine compartment for holding the engine therein, and a ventilation system for ventilating the engine compartment.
2. Description of the Related Art
A known outboard motor disclosed in, for example, JP 9-254883A includes an engine, an engine cover forming an engine compartment for holding the engine therein, a generator disposed in the engine compartment, and a ventilation system for discharging air in the engine compartment to the outside of the engine compartment through an air exit passage opening to the outside of the engine compartment.
Another known outboard motor disclosed in JP 2002-240790A includes a generator disposed in an engine compartment and having a housing provided with an inlet passage through which cooling air for cooling the generator flows into the generator, and an air outlet through which the cooling air that has worked for cooling the generator flows to the outside of the generator.
In an outboard motor having an engine disposed in an engine compartment, hot air that has worked for cooling the engine in the engine compartment flows upward in the engine compartment. Therefore, air of a comparatively high temperature collects in an upper space in the engine compartment. If air in the engine compartment flows upward, through an air passage having an inlet opening facing downward, into a fan for forcing air out of the engine compartment, air in an upper space extending above the fan cannot be efficiently sucked by the fan.
It is desirable to form an air discharge passage through which the fan discharges air to the outside of the engine compartment in a shot length. The short air discharge passage is effective in forming an engine cover defining the engine compartment in small size and forming the outboard motor in small size.
In an outboard motor provided with an engine and a generator placed in an engine compartment, part of air taken into the engine compartment is used for cooling the generator. Air that has worked for cooling the generator is hot air of a comparatively high temperature. If such hot air diffuses in the engine compartment, intake air for combustion in the combustion chamber of the engine is heated and, consequently, the volumetric efficiency of the engine decreases. Therefore, it is desirable to quickly discharge hot air that has worked for cooling the generator and hot air heated by the engine in the engine compartment from the engine compartment.
The present invention has been made in view of those problems and it is therefore an object of the present invention to improve the efficiency of ventilation of an engine compartment holding an engine included in an outboard motor and to improve the effect of ventilation air on cooling the engine and suppressing temperature rise of the engine compartment.
Another object of the present invention is to form an engine cover in small size and to build an outboard motor in small size by forming an air discharge passage of a ventilation system in a narrow range in an engine compartment.
A further object of the present invention to improve the effect of ventilation air for ventilating an engine compartment enclosing an engine and a generator, on cooling the generator and on suppressing temperature rise of the engine compartment by making a fan suck efficiently air that has worked for cooling the generator, to form the engine cover in small size and to build the outboard motor in small size by guiding air that has worked for cooling the generator by a small, lightweight guide structure.